diff --git a/Lib/urllib2.py b/Lib/urllib2.py
index 75583e3..3e700a9 100644
--- a/Lib/urllib2.py
+++ b/Lib/urllib2.py
@@ -817,6 +817,8 @@
                 h.putheader(*args)
         for k, v in req.headers.items():
             h.putheader(k, v)
+        # httplib will attempt to connect() here.  be prepared
+        # to convert a socket error to a URLError.
         try:
             h.endheaders()
         except socket.error, err: